Process of removing ash-forming constituents from a residual petroleum oil



F. M. ARCHIBALD PROCESS OF REMOVING ASH-FORMING CONSTITUENTS OLEUM OIL 1936 May 9, 1939.

FROM 1}}? ID UAL PETR Nov. 28,

.S DIuM .soar .SOLurzoN [NI-l T AG'IT'A TOR Pun/Flap 0/1. our'LeT' Patented May 9, 1939 PATENT OFFICE PROCESS OF REMOVING ASH-FORMING OONSTITUENTS FROM A RESIDUAL PE- TROLEUM OIL Francis M. Archibald, Elizabeth, N. J., assignor to Standard Oil Development Company, a corporation of Delaware Application November 28, 1936, Serial No. 113,103

4 Claims.

This invention relates to a process for the separation and purification of residual oils obtained from soaps or sludges that are produced in the refining of petroleum oils. A particular object of this invention is the purification of the residual oils of ash-forming substances.

In the refining of petroleum oils, there are formed residual oils which contain mineral substances in solution or suspension-which, upon the combustion of the oil, deposit ash and coat the furnace walls and boiler surfaces. These oils are obtained both in the acid treating of the oil and also when the oil is treated with an alkali solu tion or with doctor solution (sodium plumbite).

Generally, any of the soaps that result on refining a petroleum oil distillate contain ashforming substances. These substances have, in the past, been washed out by the use of warm water, but in many instances due to emulsions forming, the use of hot water was not practical, as these emulsions that were formed were very stable and did not break even on standing for prolonged periods of time. The soaps are sometimes removed with an alcoholic wash liquor from which a residual oil, high in soap and high in ash, isobtained after distilling ofi the alcohol. The residual oil also contains as high as 50% of water emulsified in it.

According to this invention, it has been found that emulsions may be broken and the residual oil that is separated is substantially free of ash forming constituents, as well as substantially free of water.

A preferred method of operating the present invention is shown in the accompanying drawing which diagrammatically illustrates the process. For illustration only, the purification of a sodium soap produced on treating oil with alcohol is described. This method is not to be limited to the purification of the oil-soluble sulfonates, which are obtained thereby, but may be used also to remove the ash-forming constituents from water-soluble sulfonates and other residual oils that are obtained in the refining of petroleum oil and are generally used as a fuel oil.

' With reference to the drawing, numeral l indicates a pipe for passing the sodium soap solution into an agitator 2. This sodium soap solution is generally curdy and when dried for burning contains about 4% of ash and therefore cannot be burned economically. Agitator 2 is provided with a stirring device 3 and a closed steam heating unit 4 adapted to raise the temperature to the desired levels. Into this agitator is also passed through pipe 5 provided with valve 6 a sludge obtained by treating a petroleum oil with strong sulfuric acid and which contains free sulfuric acid. A sufficient amount of this sludge is added so that upon dilution with the moisture in the sodium soap solution, an acid of about 50% strength is obtained which readily separates from the organic material on being heated to a temperature of about 150 F. and below the boiling point of the dilute acid. These two solutions, after being mixed and raised to the required temperature, are passed through pipe 1 provided with valve 8 into decanter 9 where two layers, one of oil and one of dilute acid, are obtained. Decanter 9 is provided with a baflie l and an outlet pipe ll, which is provided with a valve l2 and a vent pipe l3. The removal of the separated acid is regulated by means of gravity, that is, the acid outlet pipe is at such a level that a substantial amount of acid is retained in the decanter 13.

The separated oil is removed through pipe [4 from the upper oil layer to an agitator I5, which is provided with a stirring device 16. Into this agitator I is also introduced acid sludge by means of pipe ll. Only sufficient of this acid sludge is added that the remaining moisture in the separated oil will dilute the free acid to about 50% concentration. Heating means may be provided to maintain the acid and separated oil at the desired temperatures. The mixture of acid sludge and oil is then passed'through pipe I8 provided with valve 19 into decanter 20. Decanter 20 is provided with a. baffle 21. A valved acid outlet pipe 22, provided with vent 23, is used to remove the acid from the bottom of the decanter. The separated purified oil is removed through pipe 24 provided with valve 25 to storage for commercial use. The separated acid from decanter 20 may be returned to agitator 2 or agitator l5 by means of pump 21 and line 26, which is provided with valves 29 and 28.

According to this apparatus, only two treatments of the sodium soap solution are shown. If desired, more means of treating the sodium soap solution may be provided, though it was found that substantially all the ash-forming constituents are removed by two treatments and the oil thereby obtained may be burned without any substantial quantity of ash resulting. It is not necessary that acid sludge alone be used, as the separated acid may be used in its place, although it is required to use an acid of above 45% concentration so that on contacting with the material that is to be purified, the acid that separates will be above 40% concentration. This process is particularly applicable where the ash forming constituents are water-soluble sulfonates and where sulfonic acids in the final fuel oil are allowable. Another advantage obtained by the use of acid sludge is that the aciid sludge is also broken up into its component parts, that is, into oil, sulfonic acid, and dilute sulfuric acid.

It is obvious that the treatment of alkaline sludges from doctor treating or other high ash residual oils with acid sludge will remove the ash in the dilute sulfuric acid which separates.

The dilute acid recovered may be concentrated by the usual means. The salts, being practically insoluble in the concentrated acid, separate out and do not interfere with the reuse of the acid for treating purposes.

Emample.Residual oil containing 33% sulfonates, 15% oil, 37% water and salts was treated with a one-third volume of acid sludge. The ash was reduced from 9% to 1.4% by this treatment. The water in the product was 8.0%.

While a preferred embodiment of the invention has been shown and described, it will be understood that various modifications can be made therein within the scope of the invention, and such modifications are intended to be covered by the appended claims.

I claim:

1. The process of removing ash-forming constituents found present in residual petroleum oils containing soaps dissolved therein which were formed in the chemical treatment of said petroleum oils with sulfuric acid followed by a wash with an aqueous solution of an alkali, which comprises contacting the residual oil containing mineral substances in solution and an acid sludge in quantities sufficient so that the separated acid is of about 45% to about 50% concentration, subjecting the mixture to heat and separating the oil and dilute acid.

2. The process for removing ash-forming constituents from a residual petroleum oil containing mineral substances in solution obtained by washing an oil that had been sulfuric acid treated and neutralized with alcohol containing an alkali in solution, which comprises adding to the alcohol-extracted alkaline reacting solution an acid sludge obtained on treating a petroleum oil with sulfuric acid in amounts sufficient so that the separated acid is of about 50% concentration, subjecting the mixture to heat and separating an oil and dilute sulfuric acid.

3. The process for removing ash-forming constituents from residual petroleum oils containing in solution sodium soaps produced on washing sulfuric acid-treated petroleum oils which had been neutralized with sodium hydroxide with alcohol, which comprises adding to the sodium soap solution sufficient sulfuric acid so that the separated acid thereby obtained is of about 50% concentration, heating the mixture to a temperature of about 140 F. and separating an oil and dilute sulfuric acid.

4. The process of removing the ash-forming constituents from residual petroleum oils containing in solution a sodium soap solution according to claim 3 in Which the sulfuric acid added is in the form of an acid sludge resulting from the sulfuric acid treatment of a petroleum oil.

FRANCIS M. ARCHIBALD. 

